Thermionic detector.



H. DE P. ARNOLD. THERMIONIG DETECTOR.

APPLIOATION FILED JUNE 8, 1914.

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HAROLD DE FOREST ARNOLD, OF ORANGE, NEW JERSEY. ASSIGNOR TO WESTERN ELECTRIC COMPANY, OF YORK, N. Y., A CORPORATION OF ILLINOIS.

Timnmomc nE'rEcron.

Application filed June 8, 1914 Serial No. 848, 807.

To all whom it may concern:

' Anson), a citizen of theUni'ted siding at East Orange, in the county of Essex and State ofNewiJersey, have 1nvented certain new and useful Improvements in Thermionic Detectors, of which the following is 'a 'full, clear, concise, and exact description. t

This invention relates to thermionlc detectors for rectifying and amplifying alternating currents, and particularly feeble electrical oscillations, and its object is to increase the efliciency of such devices.

With the audion, WhlCllll S a typical thermionic device extremely sensitive to feeble L currents, it is usual when applying 1t to wireless telegraphy to connect the input electrode or grid directly or indirectly'to the antenna, and the output"electrode or plate directly or indirectly to a receiving instrument. In such use of the audion, local input and output circuits are ordinarily provided, and there is normally flowing across the space between the heated cathode or filament and the output electrode a considerable current, whiclijis'induce d by a battery or other direct current source in the local output circuit.

According to this invention, there is provided a thermionic detector, preferably'of the audion type, having a pair of input electrodes similarly connected to the negative pole of a source of current in the local input circuit and oppositely connected to the source-of current to be detected. By connecting the input electrodes to the negative pole of the source of current, which may be small, in this input circuit, and by initially adjusting the potentials of this source and of the source of current inthe output circuit, so that only a small current is normally flowing to the plate, the operation of the audion when feeble electrical impulsesare received, is such that the successive impulses, positive and negative, of the alternating current waves, are alternately but cumulatively rendered efiective to produce in the output circuit a unidirectional current of enormously greater energy than that consumed from the alternating current received.

The audion structure which has been found best adapted for the purposes of this invention is one in which the heated cathode or filament has two separated parts or arms,

Specification of Letters Patent.

Patented Feb. 16, 1915.

midway between which is the output electrode or plate, and adjacent to each of which is one of the input electrodes or grids.

Preferably the two input electrodes are connected to'opposite'terminals of asecondary winding-of a transformer, and the negative pole of the input battery isconnected to a mid pomt inthis winding. The primary winding of the transformer is then connected to the line or antenna which receives the alternating currentto be detected.

The invention will be more fully understood by reference to the accompanying drawing which illustrates the structure and gircui't'fof 'an'audion embodying the inven- The detector comprises a vacuum containing vessel 1 inclosing 'a cathode or filament of two parts or arms 2 and 2, a pair of input electrodes 3 and 3", which maybe in the form of grids or the like, each preferably closely situated with respect to one of the cathode arms, and a plate 4 symmetrically located or midway between said arms. The input electrodes are preferably situated, as shown, between the filament and-plate. The two filament'ai'ms 2 and 2 are electrically connected at their upper ends by the wire '5 and are heated by current from the battery 6. The plate 4: is connected to the positive pole of a battery 7 and the primary winding '8 of arepeating coil 9, the'jlocal output circuit being completed by way of the filament arms 2 and 2? and the spaces between them and the plate 4. The input electrodes 3 and 3 are connected to opposite terminals of a windinglO of a repeating coil 11, which thus servesi'as the sou'rceof alternating current to be detected. The midpoint ofthe windinglO is connected to the negative pole of a a'ttery 12, which maybesmall, the local input circuit being completed-by way of the filament arms 2 and 2, and the spaces, preferably very short, between them and the two input electrodes 3 and 3 The input reing device which may be a telephone re-' ceiver 15;

The operation is as follows: There exists at the filament arms 2 and 2 of the cathode, electric fields controlled jointly by the positive output electrode 4 and the negative in- ,trodes, which are located prefera arms. Now if the potential of either input electrode becomes more negative, the current from the filament to the plate can do no more than fall to zero, since the unilateral conductivity of the space will not allow a current in the opposite direction. Therefore, the decrement of current in the local output circuit due to this change is very small. If, on the other hand, the potential of the input electrode is negatively diminished, the current to the plate is increased by a considerable amount. Nevertheless, no current except the very small amount possibly admitted by the electrostatic capacity between the input electrodes and filament can flow in the input circuit, and no energy from the source to be detected except the small loss inherent in the transformer 11 is consumed in causing the direct current to flow in the output circuit. This results in energy from the battery 7 becoming available as continuous current in the output circuit so long as either input electrode is less negative than its normal, which condition is practically continuous, due to the opposition connection of the two input electrodes to the source of alternating current 10. Inshort, an alternating current potential supplied between the input electrodes 3 and 3 results in direct current in the output circuit. The value of this direct current varies as the strength of alternating potential impressed on the input electrodes, and the energy thus made available in the output circuit is enormously greater than that consumed from the electrical oscillations received.

What is claimed is:

1. In a thermionic detector, the combination with a source of current to be detected and local input and output sources of current, of a pair of input electrodes similarly connected to the negative pole of the local input source of current and oppositely connected to the source of current to be detected.

2. In a thermionic detector, the combination with a source of current to be detected Lieaeeo and local input and output sources of current, of a pair of input electrodes similarly connected to the negative pole of the local mput source of current and oppositely connected to the source of current to be detected, the potentials of said local sources of current being proportioned to admit of only a small current normally flowing from the local output source of current.

3. In a thermionic detector, the combination with the cathode and a positivelycharged output electrode and local circuit therefor, of a pair of negatively-charged input electrodes, the normal potentials of said output and input electrodes being pro ortioned to admit of only a small current owing in the local output circuit, and a source of alternating current to which said input electrodes are oppositely connected.

4:. In a thermionic detector, the combination of a cathode comprising two parts, an output electrode symmetrically located with respect to, said parts, a pair of input electrodes located adjacent said parts respectively, a source of current to be detected,

means for producing normally a small negative charge on said input electrodes, and opposite electrical connections between said input electrodes and the said source of current to be detected.

5. In a thermionic detector, the combination of a cathode comprising two parts, an output electrode located midway between said parts, a pair of input electrodes located adjacent said parts respectively, and between said parts and said output electrode, and means for producing normally a small negative charge on said input electrodes.

6. A thermionic detector comprising a cathode of tWo parts, an output electrode symmetrically located with respect to said parts, a pair of input electrodes located adjacent said parts, means for producing a small negative charge on said input electrodes, and means for producing on said output electrode a positive charge proportioned with respect to the charge on the input electrode to admit of only a small current normally flowing between said cathode and said output electrode.

In Witness whereof, I hereunto subscribe my name this 5th day of June A. D, 1914.

HAROLD DE FOREST ARNOLD.

Witnesses:

R. OLSON, W. FENTON. 

